This week on HST

HST Programs: November 19 - November 25, 2007

Program Number Principal Investigator Program Title Links
10583 Chris Stubbs, Harvard University Resolving the LMC Microlensing Puzzle: Where Are the Lensing Objects ? Abstract
10798 Leon Koopmans, Kapteyn Astronomical Institute Dark Halos and Substructure from Arcs & Einstein Rings Abstract
11082 Christopher Conselice, Univ. of Nottingham NICMOS Imaging of GOODS: Probing the Evolution of the Earliest Massive Galaxies, Galaxies Beyond Reionization, and the High Redshift Obscured Universe Abstract
11101 Gabriela Canalizo, University of California - Riverside The Relevance of Mergers for Fueling AGNs: Answers from QSO Host Galaxies Abstract
11103 Harald Ebeling, University of Hawaii A Snapshot Survey of The Most Massive Clusters of Galaxies Abstract
11109 Jian-Yang Li, University of Maryland Characterization of the UV absorption feature in asteroid (1) Ceres Abstract
11126 Kristin Chiboucas, University of Hawaii Resolving the Smallest Galaxies Abstract
11128 David Bradley Fisher, University of Texas at Austin Time Scales Of Bulge Formation In Nearby Galaxies Abstract
11130 Luis Ho, Carnegie Institution of Washington AGNs with Intermediate-mass Black Holes: Testing the Black Hole-Bulge Paradigm, Part II Abstract
11134 Karen Knierman, University of Arizona WFPC2 Tidal Tail Survey: Probing Star Cluster Formation on the Edge Abstract
11143 Andrew J. Baker, Rutgers the State University of New Jersey NICMOS imaging of submillimeter galaxies with CO and PAH redshifts Abstract
11175 Sandra M. Faber, University of California - Santa Cruz UV Imaging to Determine the Location of Residual Star Formation in Galaxies Recently Arrived on the Red Sequence Abstract
11176 Andrew S. Fruchter, Space Telescope Science Institute Location and the Origin of Short Gamma-Ray Bursts Abstract
11178 William M. Grundy, Lowell Observatory Probing Solar System History with Orbits, Masses, and Colors of Transneptunian Binaries Abstract
11196 Aaron S. Evans, State University of New York at Stony Brook An Ultraviolet Survey of Luminous Infrared Galaxies in the Local Universe Abstract
11197 Peter Garnavich, University of Notre Dame Sweeping Away the Dust: Reliable Dark Energy with an Infrared Hubble Diagram Abstract
11211 George Fritz Benedict, University of Texas at Austin An Astrometric Calibration of Population II Distance Indicators Abstract
11216 John A. Biretta, Space Telescope Science Institute HST / Chandra Monitoring of a Dramatic Flare in the M87 Jet Abstract
11218 Howard Bond, Space Telescope Science Institute Snapshot Survey for Planetary Nebulae in Globular Clusters of the Local Group Abstract
11222 Michael Eracleous, The Pennsylvania State University Direct Detection and Mapping of Star Forming Regions in Nearby, Luminous Quasars Abstract
11225 C. S. Kochanek, The Ohio State University Research Foundation The Wavelength Dependence of Accretion Disk Structure Abstract
11289 Jean-Paul Kneib, Laboratoire d'Astronomie Spatiale SL2S: The Strong Lensing Legacy Survey Abstract

Some selected highlights

GO 10798: Dark Halos and Substructure from Arcs & Einstein Rings

Hubble imanges of Einstein ring gravitational lenses Gravitational lensing provides a powerful method of tracing the mass distribution of individual galaxies and galaxy clusters; at the same time, the amplified the light from background galaxies provides a means of probing the early stages of galaxy formation. The Sloan Digital Sky Survey (SDSS) has proven a powerful tool for identifying new lens candidates, although high angular resolution HST observations are essential for confirming those candidates as genuine gravitational lensing systems (see Program GO 10886). The present program focuses on that sample, targeting confirmed lenses for deep, multicolour imaging that aims to measure the overall mass distribution of the lens galaxies, and quantify the existence of small-scale sub-structure. The current cosmological paradigm, cold dark matter, predicts that sub-clustering within galactic halos should scale with increasing redshift; observations of lenses at different redshifts will serve to test this prediction.

GO 11109: Characterization of the UV absorption feature in asteroid (1) Ceres

HST images of Ceres The asteroid Ceres has undergone more changes in classification than most astronomical objects. Discovered by Giuseppe Piazzi on New Year's day 1801, Ceres was first identified as a planet lying between Mars and Jupiter (consistent with the Titius-Bode sequence). It soon became clear that Ceres was much smaller than any known planet (a diameter of only 950 km), and William Herschel suggested that it should be called an "asteroid" (star-like body), since it was unresolved in telescopes of the time. Within 6 years. Pallas, Juno and Vesta had been added to the roster, and the descriptor "minor planet" was applied. Most recently, Ceres has changed status again, becoming, with Pluto, a "dwarf planet", the only such body within the asteroid belt. Nomenclature apart, observations of Ceres can provide important insight into the chemical composition of the bodies within the main asteroid belt. Ceres and Vesta will be targeted by the NASA Discovery Mission, Dawn, launched on 27 September this year. The present proposal aims to use the objective prism on the ACS/Solar Blind Channel to obtain uv spectra covering the wavelength range 1200 to 2000 Angstroms. The prime goal is to obtain an improved characterisation of a broad absorption feature residing at these wavelengths, and obtain a better understanding of its origin.

GO 11175: UV Imaging to Determine the Location of Residual Star Formation in Galaxies Recently Arrived on the Red Sequence

Galaxy mergers and the red sequence

The overwhelming majority of galaxies are found in clusters. Observations show that almost all well-defined cluster systems at low and moderate redshift have a significant population of elliptical galaxies which have red colours, indicative of old stellar populations and minimal current star formation. The elliptical galaxies outline a distinct sequence in the colour-magnitude (or colour-mass) diagram, the so-called red sequence. Over the last few years, there has been considerable interest in understanding the origins of this sequence: how did the ellipticals form (most theories envisage mergers of gas-rich systems at moderate redshifts)? when did star formation cease in these galaxies (most galaxies in clusters at redshifts 1.5 < z < 3 seem to have active star formation)? are there environmentally-dependent effects? This proposal aims to address some of these questions through WFPC2 BVI and ACS/SBC observations of a number of low-redshift (0.04 < z , 0.10) galaxies that appear to have only recently arrived on the red sequence. The WFPC2 data will provide detailed morphologies, while the SBC ultraviolet imaging will be ued to search for traces of residual star formation.

GO 11225: The Wavelength Dependence of Accretion Disk Structure

The first Einstein cross, the gravitational lensed QSO, G2237+0305 Gravitational lensing is a consequence the theory of general relativity. Its importance as an astrophysical tool first became apparent with the realisation (in 1979) that the quasar pair Q0957+561 actually comprised two lensed images of the same background quasar. In the succeeding years, lensing has been used to probe the mass distributions on a variety of scales: of galaxies (primarily via multiply-imaged quasars); of galaxy clusters (arcs and arclets); and at the largest scales (weak lensing). However, lensing can also provide insight on the small-scale properties of the object being lensed. In a lensed QSO, the light from the QSO follows different paths to produce the separate images; each of those paths has a different length; consequently, flux variations in the source show up at different times in the separate images. The present program aims to take advantage of this property to probe the structure of the accretion disks surrounding the central black hole in a number of lensed QSOs. The program will combine ultraviolet observations with the ACS/SBC on HST with Chandra X-ray data. Studying the variation as a function of wavelength should probe the accretion disk structure, since light from the inner regions are expected to dominate at shorter wavelengths, while the outer regions dominate at longer wavelengths.

Past weeks:
page by Neill Reid, updated 7/11/2007